pean and other countries at an earlier period. Since the countries of the less developed world are often beginning reduction in the birth rate at a much higher level than European countries, a comparison is made for the years required for the crude birth rate to decline from 35 to 20 at different periods. A crude birth rate of 35 was chosen to eliminate fluctuations in natality unrelated to the widespread adoption of family limitation. In no country entering the transition since 1950 has the birth rate dropped to 20. In these cases the decline in the birth rate to 20 was projected by linear extrapolation of annual average percent reduction actually experienced after reaching the 35 level.
In a number of countries (for example, Australia, Canada, New Zealand, and the United States) the birth rate fell to 20 or below in the initial period of decline, but later returned to somewhat higher levels in the postwar "baby boom." Some of these countries now again have birth rates below 20, but the years in transition were considered only for the initial period of consecutive downward trend.
From Table 2 it will be seen that the average length of time required for a country to pass through this stage of demographic transition has been greatly reduced, from some 50 years for countries entering the transition in 1875-99 to half that time or less for those countries entering the transition, so defined, since 1950.
The limited number of countries and years of experience included in Table 2 restricts the conclusions that may be drawn from it. Because the new surge of natality reduction is so recent, relatively few countries were eligible, but all were included.* However, the wider experience reflected in Table 1 supports the evidence, which in any event represents a continuation of historical trends.
An obvious question is whether the countries that have-entered this phase of the natality transition since 1950 will in fact reach birth rates as low as 20, or fertility as low as that achieved in European countries. All that may be said is that as yet there is no indiction of a "floor" above those levels. Three of the countries in Table 2 already have birth rates in the lower 20's. At present rates of fertility decline the matter will soon be put to empirical test.
Although the "new" countries may move more rapidly through the transition as defined above, they also have farther to go because their initial birth rates are higher. It therefore seems desirable to compare overall experience
*A11 countries meeting the following criteria were included: (a) over one million population; (b) initiation of continuous decline in birth rate prior to 1960; (c) at least 5 years of birth rates at 35 or below. A number of smaller countries and additional larger countries with more recent fertility declines at higher levels also show much more rapid rates of reduction in the birth rate than were historically recorded for European countries. Among these are Albania, Barbados, Costa Rica, Malaya, Mauritius, Reunion, Trinidad and Tobaeo and several constituent republics of the U.S.S.R.